Front Wheel Vibration or shimmy is
a very common complaint by Morgan owners. Identifying which of the various
front suspension components is causing these vibrations can be very frustrating.
To try to ease some of this frustration, I will talk you through the steps
of isolating and fixing the problem.

Tires and Rims

CHECKING THE TYRE PRESSUREThe first and easiest check is tire pressure. For earlier
4/4s, it should be 16 to 18 pounds, for Plus 8s 20-22 (add 3-4 pounds
for high speeds driving. If in doubnt, check your Manual.

CHECKING THE RIMS Next comes
the possibility that a is "out of round". This condition is more prevalent
in the cars fitted with wire wheels but if a disk wheel has had a brush with
a curb, it too can be warped. The procedure to check the tires and wheels
is similar and simple. Jack up far enough to get the desired wheel off the
ground.

Place the brick along side the wheel and move the pointer
so it is perpendicular to the wheel. You want the pointer to just touch the
rim where it rolls in - where the bead seats. Again spin the wheel and watch
for variations in the gap between the pointer and the rim. If the gap is
less that 1/8" the rim is OK. If the gap is greater than 1/8" the wheel will
have to be trued - especially so for wire wheels. For disk wheels,
the wheel is usually replaced.

CHECKING THE TYRES, place brick just
in front of the tire. On the brick place a screwdriver (or something) to be
used as a pointing device. Slide the pointer towards the tire, until it just
touches. Now slowly rotate the wheel. As the tire passes the pointer watch
the gap between the pointer and the tire. If there is a "hi" spot the tire
will push the pointer back onto the brick. At the low spot on the tire, you
will see the widest gap between the tire and the pointer. If this gap is
less than 1/8" the tire is OK.

With the car sitting on the ground at normal ride height,
have a friend grab the top of the front wheel and push inward toward the center
of the car and then pull outward away from the car. This must be done with
some degree of force. While your friend is doing this, take a bright light
and look carefully at the point where the spindle rests on the top of the
rebound spring (that is the small lower spring at the bottom of the kingpin).

You are looking for side to side movement at this point.
This is where most wear occurs on the kingpin. With unworn parts there will
be no movement here, and the greater the usage the more the movement. More
than 1/8 inch of play at this point is an indication of worn out bushings
and probably kingpins also. 1/8 inch of wear at this point probably equals
about 1/2 inch or more of movement at the edge of the tire.

Movement at the edge of the tire can also indicate play
in the front wheel bearings. That is why it is important to look at the interface
of the rebound spring and spindle to ascertain exactly where the play is
located.

With the car on the ground and front wheels facing straight
ahead, grab the tread at the top of tyre with your fingers try to push and
pull in and out.. Do you feel a significant movement (a slight click can
be ok) . If the movement is excessive, you should check the adjustment of
the castle nut holding the bearing. To adjust the castle nut, you remove its
cotter pin and then tighten until it makes just contact with the bearing and
then back OFF to first cotterpin hole. (WATCHPOINT: If you tighten the castlenut
too tightly against the bearing, you will quickly burn the bearing.)

CHECKING THE DAMPER BLADES To
test for wear, with the car on the ground, grab the blade and push forward
and back. If a click or movement can be heard or felt the shims need to be
pushed tight against the blades to prevent that. However, there MUST be free
movement in and out of the slot made by the shims. Push down on the blade
to see if it can move in and out.

Wheel Cracks

There are two places where disc steel wheels "normally"
crack, firstly, at the lug nut and secondly, at the hub cap attaching
stud. Cracking at the lug nut is not caused by over tightening the lug nut,
but rather by the stress to the wheel induced by the stiff sliding pillar
suspension under racing conditions. The factory also introduces stresses
at this location by stamping the wheel to provide full purchase for the sloped
shape of the wheel lug nuts. Lastly, wheel stresses are also magnified by
the fact that these wheels have only four lug nuts, a 20% increased loading
factor on each nut over normal five studded wheels.

The crack at the hub cap studs is due to the factory induced
stress when the curved portion of the wheel is flattened for insertion of
the hub cap stud. These cracks then radiate to the ventilation holes in the
wheel. An appropriate solution is to have a competent and experienced welder
weld 1/8 inch flat plates to the back side of the wheel with appropriate
holes for the lug nuts and the center hub.

BalancingYour Wheels

With these items checked it's time to head down to the
local tire shop and have your wheels dynamically (spin) balanced. Most shops
take the wheel and tire off the car to balance it.. It requires a special
adapter, so check with the shop to ensure that they have the adapter.) The
advantage here is that the wheel/tire unit can be moved around to any of
the 4 axles and maintain its balance.

Sometimes the suspension components can add to the balancing
problems. To try to balance the entire suspension you will have to find a
shop that can still spin balance the wheels on the car. But this seem to
have passed on to oblivion like so many other things. This method will give
you a better balance at each corner but the wheels and tires can not be moved.
When the tires are rotated, the suspension will have to be re-balanced.

Wheel Bolt Torque

Thread Size

lbs / ft

Kg / mtr

3/8 UNF

38 - 40

5.2 - 5.5

7/16 UNF

53 - 55

7.3 - 7.6

1/2 UNF

77 - 79

10.6 - 10.9

M12 x 1.25

65 - 67

9.09 - 9.20

Front Vibration (Curing it when all else fails)

Webmaster Note:
There is plenty in these pages that
will show how to sort ANY stock Morgan front suspension and
rid it of vibration.
In theory..and happily most often in practice, these pages can
cure any issue in the original Morgan manner. However, for whatever the
mysterious reasons, sometimes vibration will be beyond the skills of
the owner or various addons or changes he may have made. It such cases
the cars become a source of
deep frustration. The point of this Manual is not to force you to sort
your
Morgan as it was originally meant to be. The priority is to help
you reap enjoyment, not frustration
from your mog. For those of you with front end vibration that resists
your
efforts, here is a quick fix to stop vibration and get you back on
the
road. You can always renew your efforts for the proper cure at your leisure.
And if someone sees this non-Morgan solution and takes you to task,
direct them here and beat them on the head with your knock-off hammer.
That's what it's for. Enjoing your Morgan is more important than being
correct.

Lorne,I wanted to wait until the traffic died down before I wrote.
eMog was good to me and I thank you for it. I wanted to let you know that
my St. Malvern's dance is gone. I made lower adjustable braces, but with
them I was only able to limit the shake to a very narrow critical speed (about
45 MPH) or make it much worse depending on how I had them adjusted. At the
worst, I was able to make the shake occur at 60MPH accelerating, and then
shake again at 40MPH decelerating. I could not rid the car of the stroke
of 5 1/4 inches (same as a VW beetle damper) and my car requires 5 3/4 inches
for the steering to go fully right and left, so I have ordered a damper for
a Mercedes SLK or Chrysler Crossfire which has a longer stroke. I should
have that installed in the next month, but I'm in no hurry since I can now
drive the old car. Caster certainly plays a part, but adding the damper worked
like magic. I cannot detect it as far as steering effort goes, and the only
side effects are the good feeling steering and no shake. I'll send you a
picture of the Mercedes unit when I get it fitted. In the meantime, these
are pics of the VW unit installed. I used some very stiff alloy 3/16" aluminum
flatbar mounted to the lower rad mounts. The rad is still mounted as before
on rubber with the nylock nuts only snugged up enough to compress the rubber
a little, but the forward bolts are tight to hold the flatbar in place. When
I install the Merc unit, I will have to mount it more to the right of the
car, and about 1-1/2 inches forward so that it does not foul the steering
rod on large bumps. I am now of the opinion that those old cars should have
come with a damper. :-)

Three weeks later!!!

Lorne, I hope all is
well with you. My aftermarket Mercedes SLK (also fits Chrysler Crossfire)
steering damper arrived and I mounted it. As I predicted, I had to mount the
fixed end slightly forwards of the aluminum plate to prevent the steering
rod from contacting it on hard right hand bumps. This time I also mounted
the damper correctly so that the dust cover would not collect water. The previous
photos of the VW bus damper show how NOT to do it. This damper works even
better than the VW unit. It has plently of travel with some to spare so that
the wheels will turn fully to the steering stops. Also, this damper is slightly
stiffer, but not so stiff as to be noticeable when turning the steering wheel,
but stiff enough to completely damp the steering vibration. With the VW damper,
the critical speed at which the St Malvern Dance occurred could be felt,
although the dance never started. With the Mercedes damper, running the car
up and down through that critical speed reveals no evidence that there is
a critical speed at which vibration occurs. Here's a couple of pictures of
the installation and the parts I used. Take care, Meyle part number
026 046 0161